In many electronics applications, an analog input signal is converted to a digital output signal (e.g., for further digital signal processing). For instance, in precision measurement systems, electronics are provided with one or more sensors to take measurements, and these sensors may generate an analog signal. The analog signal would then be provided to an analog-to-digital converter (ADC) as an input to generate a digital output signal for further processing. In another instance, an antenna generates an analog signal based on the electromagnetic waves carrying information/signals in the air. The analog signal generated by the antenna is then provided as input to an ADC to generate a digital output signal for further processing.
ADCs convert a continuous physical quantity that is also known as an analog signal to a digital signal whose values represent the quantity's amplitude (or to a digital signal carrying that digital number). An ADC is typically composed of many devices making up an integrated circuit or a chip. An ADC can be defined by the following exemplary application requirements: its power consumption, its bandwidth (the range of frequencies of analog signals that the ADC can properly convert to a digital signal), its resolution (the number of discrete levels the maximum analog signal can be divided into and represented by the digital signal), and its signal to noise ratio (how accurately the ADC can measure signal relative to the noise the ADC introduces). ADCs have many different designs, which can be chosen based on the application requirements. In many cases, it is not trivial to design an ADC that meets the application requirements while providing adequate performance. One critical limitation to the performance of an ADC is the linearity of the overall system, or the linearity of the ADC's signal path. Linearity can, for example, affect the signal-to-noise-and-distortion ratio (SINAD) and spurious free dynamic range (SFDR) of the ADC. In some cases, circuit designers achieve better linearity at the cost of implementing more complex and/or power hungry circuit designs. In some cases, non-linearity is unavoidable in certain circuit designs, for instance, due to mismatches or inherent characteristics in circuit components.